| 被动扩散式检测管是用来测定较长时间下气体浓度的时量平均值（TWA），采用自然扩散的方式。 这种检测管里面填充有吸附剂及反应剂，气体以一定的速率被均匀吸附，从而出现较为明显均匀的变色。 检测工作场所人员的有害气体暴露量时，用右图的检测管夹（710）放置在人员衣领处即可。 检测有害气体在工作场所的分布时，把该检测管固定放置一段时间后就可检测出来。也可用来进行长时间的检测。 | |
特点 简洁，轻巧，方便多用 直接读数 不需取样设备 图例 A-切断处 B-吸附剂 C-检测剂 | 检测管夹 No. 710 |
Performance
| Measuring Range | 2.5 to 1000 ppm |
| Sampling Hours | 0.5 to10 hours |
| Detecting Limit | 0.5 ppm (10 hours) |
| Colour Change | Purple → Yellow |
| Reaction Principle | 2NH3 + H2SO4 → (NH4)2SO4 |
| Coefficient of Variation | 10% (for 25 to 500 ppm-hr) |
| Shelf Life | 3 Years |
| Corrections for temperature & humidity | Temperature correction is necessary |
| Store the tubes at cool and dark place. | |
Possible coexisting substances and their interferences (NOTE)
| Substance | Concentration | Interference | Change colour by itself to |
| Amines, Hydrazine | + | Yellow | |
| Aromatic amines | No | No |
Other substance measurable with this detector tube
| Substance | Correction Factor | Sampling Time | Measuring Range |
| Dimethylamine | 0.75 | 0.5 to 10 hours | 1.9 to 750 ppm |
| N,N-Dimethylethylamine | 1.6 | 0.5 to 10 hours | 4 to 1600 ppm |
| Hydrazine | 0.65 | 0.5 to 10 hours | 1.6 to 650 ppm |
| Triethylamine | 2.1 | 0.5 to 10 hours | 5.3 to 2100 ppm |
| Calibration gas generation | Permeation tube method |
| TLV-TWA | TLV-STEL | Explosive range |
| 25 ppm | 35 ppm | 15 to 28% |
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